Chosen Solution
My iMac won’t boot up to the login screen. It gets stuck at 100%. Ive done everything I can from resetting the smc, to resetting the nvram, to redownloading macOS. I checked the disk utility and it says nothing is wrong. Ive done everything the apple support page has shown to fix it and nothing has worked.I had a friend look at it and he seems to think the hard drive might be bad. Could that cause my issues?
Boot from an external USB drive. Then run Disk Utilities from it. UPDATE 8/12/20 Here how to drop in a new SSD, see step #36 iMac Intel 27" EMC 2639 Hard Drive Replacement
First, check that your Mac has a power source. Yes, it’s silly and obvious, but anyone who’s done tech support knows that you have to get the obvious fixes out of the way first. So if your MacBook won’t boot on battery power, plug it in. The battery may be fully depleted or could be malfunctioning. Use Disk Utility From Recovery Mode. Press and hold the Command + R keys during the boot-up process. You should try to press these immediately after you hear the chime sound. Your Mac should boot to recovery mode. If it doesn’t, you probably didn’t press the keys soon enough — restart your Mac and try again.
